1. Field of the Invention
The present invention relates to a light receiver unit having a light receiving element therein that is used for a photometering device of a camera.
2. Description of the Related Art
FIG. 4 shows a conventional light receiver unit which is provided with a circuit board 1, a light receiving element (e.g., SPD [silicon photo diode]) 2, a packaging cover 3, a filter 5 and a resin (transparent thermosetting resin) 7. The light receiving element 2 that is secured to the circuit board 1 is covered by the packaging cover 3. The packaging cover 3 is provided with a window hole 4, a recessed portion 4a formed around the window hole 4, an injection hole 6 and a vent 8. A lens 9 (shown by a two-dot chain line in FIG. 4) for converging the incident light onto the light receiving element 2 is positioned adjacent to the window hole 4. The filter 5 for adjusting the luminosity factor or absorbing infrared rays is fixed to the recessed portion 4a. With the packaging cover 3 fixed on the circuit board 1, the resin 7 is injected into the packaging cover 3 through the injection hole 6 while forcing the internal air out of the packaging cover 3 through the vent 8, to thereby fill the resin 7 in the closed space (inner space) formed between the packaging cover 3 and the circuit board 1. After the resin 7 has filled up the space between the packaging cover 3 and the circuit board 1, the resin 7 is heated in order to be solidified, in order to protect the light receiving element 2. Accordingly, irregular reflection can be prevented from occurring at the window hole 4, at the boarder between the air and the resin 7, since the outer surface 5a of the filter 5 is a plane. Consequently, precision in photometering using the light receiving element 2 is improved for the spot metering, evaluative metering using a plurality of zones.
The filter 5 is usually made of a hard material such as a rigid plastic, glass etc. However, since the filter made of a hard material is difficult to manufacture, and the manufacturing method therefor being very restricted, the cost of manufacture the filter is inevitably high. Accordingly, it is preferable that a soft flexible material which can be easily processed be used as the filter 5. However, if such a flexible material is used as the filter 5, the filter 5 can be deformed due to the pressure applied thereto, generated when the resin 7 is fully injected and/or due to the expansion and contraction of the resin 7 when the resin 7 is heated in order to be solidified. This causes the outer plane surface 5a of the filter 5 to deform, which deteriorates the precision in photometering using the light receiving element 2.
The primary object of the present invention is to provide a light receiver unit having a light receiving element, wherein a soft flexible filter can be used without deteriorating the precision in photometering while increasing the degree of freedom for the selection of filter.
To achieve the object mentioned above, according to an aspect of the present invention, there is provided a light receiver unit having a packaging cover and a light receiving element positioned in an inner space of the packaging cover wherein a resin is injected into the inner space to be solidified. The light receiver unit includes: a window hole formed on the packaging cover, a filter fixed to the packaging cover to cover the window hole, and a transparent plane-parallel plate fixed to the packaging cover to cover the filter from the inside of the packaging cover, the transparent plane-parallel plate being harder that the filter; whereby the filter is protected from any pressure caused by the injected resin.
Preferably, transparent plane-parallel plate is attached to the filter.
Preferably, the transparent plane-parallel plate is apart from the filter to form a gap therebetween.
The transparent plane-parallel plate can be a bandpass filter.
Preferably, the packaging cover includes: an injection hole through which the resin is injected into the inner space of the packaging cover; and a vent through which air in the inner space is forced out of the packaging cover when the resin is injected through the injection hole.
Preferably, a circuit board is further included, on which the light receiving element is fixed, the packaging cover being fixed to the circuit board to cover the light receiving element.
Preferably, the packaging cover includes a recessed portion formed on an inner surface of the packaging cover around the window hole, the filter and the transparent plane-parallel plate being fixed to the recessed portion.
Preferably, the packaging cover includes: an outer smaller recessed portion formed on an inner surface of the packaging cover around the window hole; and an inner larger recessed portion formed on an inner surface of the packaging cover around the outer recessed portion, whereby a stepped portion is formed on an inner peripheral surface of the window hole, wherein the filter and the transparent plane-parallel plate are fixed to the outer recessed portion and the inner recessed portion, respectively.
Preferably, the thickness of the filter is smaller than the depth of the outer recessed portion to form a gap between the filter and the transparent plane-parallel plate.
Preferably, the transparent plane-parallel plate is attached to the filter so that the filter and the transparent plane-parallel plate is provided as a layered plate.
Preferably, the resin is a thermosetting resin.
The filter can be a filter for adjusting the luminosity factor, or alternatively, the filter can be a filter for absorbing infrared rays.
According to another aspect of the present invention, there is provided a light receiver unit including: a light receiving element fixed on a circuit board; a packaging cover fixed on the circuit board to cover the light receiving element, the packaging cover forming a space between the light receiving element and the cover; a resin which is injected into the space to be solidified; a window hole which is formed on the packaging cover and through which light enters the packaging cover to be incident on the light receiving element; a filter for adjusting the luminosity factor or absorbing infrared rays fitted in the window hole; and a transparent plane-parallel plate fixed to the packaging cover adjacent to the filter to tightly separate the filter from the space into which the resin is injected.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 10-224076 (filed on Aug. 7, 1998) which is expressly incorporated herein by reference in its entirety.